The polymerization of alpha-olefins to product synthetic lubrcating oils with Friedel-Craft type cationic catalysts is well known. However, these catalysts or processes have certain restrictions, such as catalyst selection limited to soluble compounds, the need for longer and uncertain induction periods, or low conversion rates of the monomer.
U.S. Pat. No. 2,525,788 (Fontana et al.) discloses high viscosity oils made from alpha-olefins. The choice of the aluminum halide is limited to AlBr.sub.3 because of its solubility in hydrocarbon solvents. Aluminum halides (e.g. AlCl.sub.3) insoluble in such solvents cannot be used. The selection and use of promoters is in variance with the findings of the present invention.
U.S. Pat. No. 2,559,984 (Montgomery et al.) discloses the use of an insoluble aluminum chloride "sludge" by a batch or continuous process. Monomer conversion is limited to 10-20%, and only by repeated recycling is it possible to obtain high viscosity polymeric fluids. The catalysts of the instant invention are in solution and produce high viscosity polymer upon contact with the monomers.
U.S. Pat. No. 3,312,748 (Johnson) discloses the use of the reaction products of triorganoaluminum or organoaluminum halides with carbon tetrachloride or an alkyl haloform as catalyst to polymerize alpha-olefins. Aluminum trihalides are excluded as catalyst components. The formation of the active products which are insoluble or partially soluble precipitates requires uncertain or extended induction periods which may be reduced by heating to elevated temperatures or by the use of a second initiator, such as titanium tetrachloride.
U.S. Pat. No. 4,041,098 (Loveless) discloses a soluble catalyst system generated in situ by the addition of one solution of an alpha-olefin containing a soluble alkyl aluminum halide to a second solution of the olefin containing an organohalide initiator. The process is capable of producing fluids having high viscosity and viscosity index values and low pour points. However, it suffers form limiting the choice of catalysts to those soluble in the monomer.